Q.164 Physics ⭐ 360° Option Elimination Active

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NEET 2020 Physics Question 164 Solution

Topic: Current Electricity · Official NTA Booklet Code E1

Question

The color code of a resistance is given below: The values of resistance and tolerance, respectively, are:

✓

Verified Against NTA Final Answer Key

Option (4) : 470 Ohm, 5%

📚 Current Electricity Easy

📋 Given Parameters & Problem Setup

Band 1 Yellow (digit 4)

Band 2 Violet (digit 7)

Band 3 Brown (multiplier 10^1)

Band 4 Gold (tolerance ±5%)

⚡

The 30-Second Exam Hall Shortcut: ⚡ "BB ROY: Yellow = 4, Violet = 7, Brown = ×10^1, Gold = ±5% => 47 × 10^1 = 470 Ω, 5%!"

⏱️ 20 seconds

Using the standard mnemonic 'B B ROY of Great Britain had a Very Good Wife': Yellow corresponds to 4, Violet corresponds to 7, Brown corresponds to multiplier 10^1, and Gold corresponds to ±5% tolerance. Value = 47 × 10^1 Ω = 470 Ω with 5% tolerance. Direct 5-second match with Option (4)!

1 1st band (Yellow) = 4.

2 2nd band (Violet) = 7.

3 3rd band (Brown) = multiplier

10^1

4 Resistance =

47 \times 10^1\ \Omega = 470\ \Omega

5 4th band (Gold) =

\pm 5\%

tolerance.

6 Select Option (4) 470 Ω, 5%.

🛡️

Why You Can 100% Trust This Shortcut: NCERT Physics · Current Electricity (Resistors: Color Coding)

📐

Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Review Carbon Resistor Color Coding System

For a 4-band carbon composition resistor: - First band: First significant decimal digit - Second band: Second significant decimal digit - Third band: Decimal multiplier ( $10^n$ ) - Fourth band: Tolerance in percentage

Step 2

Decode Bands Sequentially

- Band 1 is Yellow: Value = 4 - Band 2 is Violet: Value = 7 - Combined significant figures: 47 - Band 3 is Brown: Multiplier = $10^1$ - Band 4 is Gold: Tolerance = $\pm 5\%$ (Silver would be $\pm 10\%$ , None would be $\pm 20\%$ ).

Step 3

Calculate Resistance Value

$R = (47) \times 10^1\ \Omega = 470\ \Omega$ . Tolerance = $\pm 5\%$ .

Step 4

Match with Options

Option 4 explicitly specifies $470\ \Omega, 5\%$ .

⭐

360° Option Elimination Engine Key Feature

Diagnose every choice: Know exactly why the right option works and why distractors fail.

4-Option Deep Scan

1 A

✗ Incorrect

Verdict & Scientific Reason:

Incorrect; confuses Brown multiplier (10^1) with Yellow (10^4), giving 470 kilo-ohms.

⚠️

Student Fallacy (Why candidates pick this trap): Adding kilo-ohm prefix mistakenly.

2 B

✗ Incorrect

Verdict & Scientific Reason:

Incorrect; confuses multiplier with Orange (10^3) and tolerance with Silver (10%).

⚠️

Student Fallacy (Why candidates pick this trap): Misremembering multiplier and tolerance bands.

3 C

✗ Incorrect

Verdict & Scientific Reason:

Incorrect; confuses Brown multiplier (10^1) with Red (10^2), yielding 47 × 100 = 4700 Ω = 4.7 kΩ.

⚠️

Student Fallacy (Why candidates pick this trap): Off by a factor of 10 on the multiplier band.

4 D

✓ 100% Correct

Verdict & Scientific Reason:

Accurate value; Yellow (4), Violet (7), Brown (×10^1), Gold (±5%) gives 470 Ω, 5%.

💡

Why this is airtight: None; exact application of color code tables.

⚠️

NTA Trap Alert: Brown vs Black Multiplier

Black is 0 (multiplier 10^0 = 1). Brown is 1 (multiplier 10^1 = 10). Red is 2 (multiplier 10^2 = 100).

🛡️ How to avoid the -1 mark: Recite: Black (0), Brown (1), Red (2), Orange (3), Yellow (4), Green (5), Blue (6), Violet (7), Gray (8), White (9).

📖

Core NEET Syllabus Standard

Physics · Current Electricity Standard Benchmark

Core Scientific Principle Tested:

Syllabus Focus: Carbon Resistor Color Coding: Resistance and Tolerance Determination

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

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NEET 2020 Physics Question 164 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ "BB ROY: Yellow = 4, Violet = 7, Brown = ×10^1, Gold = ±5% => 47 × 10^1 = 470 Ω, 5%!"

Step-by-Step Rigorous Workflow & Mathematical Proof

Review Carbon Resistor Color Coding System

Decode Bands Sequentially

Calculate Resistance Value

Match with Options

360° Option Elimination Engine Key Feature

NTA Trap Alert: Brown vs Black Multiplier

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

🔗 Related Questions — Current Electricity

Current Variation with Temperature for Series and Parallel Dual-Coefficient Resistors

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